The history of light-emitting diodes
①In 1962, the joint laboratories of GE, Monsanto, and IBM developed a red-emitting gallium arsenide phosphorous (GaAsP) semiconductor compound. Since then, visible light-emitting diodes have entered the commercial development process.
②In 1965, the world’s first commercialized light-emitting diode was born. It was an LED that emits infrared light made of germanium. The unit price at that time was about US$45. Soon thereafter, Monsanto and Hewlett-Packard launched commercial red LEDs made of GaAsP materials. The efficiency of this LED is about 0.1 lumens per watt, which is more than 100 times lower than the 15 lumens per watt of a typical 60 to 100 watt incandescent lamp.
③In 1968, breakthroughs were made in the research and development of LEDs. The efficiency of GaAsP devices reached 1 lumen/watt by using the nitrogen doping process, and they were able to emit red, orange and yellow light.
④In 1971, the industry introduced GaP green chip LEDs with the same efficiency.
⑤By the 1970s, due to the large number of applications of LED devices in home and office equipment, the price of LED plummeted. In fact, the main market for LEDs in that era was the application of digital and text display technology.
⑥ A major technological breakthrough in the early 1980s was the development of AlGaAsLED, which can emit red light with a luminous efficiency of 10 lumens per watt. This technological advancement enables LEDs to be used in outdoor information distribution and automotive high-mount brake light (CHMSL) equipment.
⑦In 1990, the industry developed the AlInGaP technology that can provide the best red device performance, which is 10 times higher than the standard GaAsP device performance at the time.
⑧Today, the most efficient LED is made of transparent substrate AlInGaP material. From 1991 to 2001, further developments in material technology, chip size and shape have increased the luminous flux of commercial LEDs by nearly 30 times.
⑨In 1994, Japanese scientist Shuji Nakamura developed the first blue light-emitting diode on a GaN substrate, which sparked an upsurge in the research and development of GaN-based LEDs. In 1996, the white LED was successfully developed by the Japanese company Nichia (Nichia).
⑩In the late 1990s, the LED that excited YAG phosphors to produce white light by blue light was developed, but the color was uneven, the service life was short, and the price was high. With the continuous advancement of technology, the development of white light LEDs has been quite rapid in recent years. The luminous efficiency of white light LEDs has reached 38lm/W, and laboratory research results can reach 70lm/W, greatly surpassing incandescent lamps and approaching fluorescent lamps.
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